1. Field of the Invention
The present invention relates to a semiconductor process, and more particularly, to a method for removing moisture in an opening.
2. Description of Related Art
Along with rapid progress of semiconductor technology, dimensions of semiconductor devices are reduced and integrity thereof is promoted continuously to further advance operating speed and performance of integrated circuits (ICs). When the integration level of integrated circuits (ICs) is increased, surface area of a chip is not sufficient to fabricate the required interconnections in a single layer, so that a design including more than two layers of multi-level metal interconnections is adopted in the VLSI technology. The dual damascene process is a widely used metal interconnection technology due to the advantages of improving device reliability and enhancing throughput.
As the demand for the device integrity is raised, dramatic changes in physical properties, such as contact resistance among the device components, have to be considered so as to avoid a great impact on the operating speed and performance of the circuit. Taking an existing fabrication of a dual damascene structure as an example, after formation of a barrier layer but before a subsequent step, there is generally an idle time such that moisture or minor impurities are prone to be trapped on the barrier layer in the opening. Thereafter, the opening is filled with metallic copper (Cu) material in the subsequent procedure. Since the moisture is trapped in the opening, defects, e.g. voids in the resultant copper material, are usually caused by the following thermal treatment, thereby increasing the contact resistance and unfavourably impacting on the device performance.
As a result, how to effectively prevent the defects of the material filling in the opening and ensure device characters is one of the immediate issues to be solved in the art as critical dimensions of the opening is miniaturized, so as to expect improvements in the process reliability and the device performance.